Rapid co‐transport of sodium and chloride ions in giant salivary gland cells of the leech Haementeria ghilianii.

Abstract

SUMMARY1. Double-barrelled Cl--selective microelectrodes were used to measure the apparent intracellular Cl-activity (a',) and membrane potential (Em) of leech salivary gland cells. In standard physiological solution buffered with HEPES (10 mM), intracellular Cl-activity (corrected for interference) was 38 + 8 mm (n = 11) compared to a value of 12-8 mm expected for passive Cl-distribution. The mean Em was -49*4+ 8-2 mV (n = 21) which was about 27 mV negative to the Clequilibrium potential.2. Removal of external Cl-led to a slow fall in a', until a steady-state level of 4-11 mm was reached in 30-60 min. Recovery of a', on readdition of external Cltook only 2-3 min. The uptake followed an exponential time course having a single rate constant of 1-73 + 0-1 min' (n = 5) whereas the loss appeared to occur in two phases. Changes in external Cl-produced immediate changes in Em which were the opposite of those expected for a high Cl-permeability, i.e. Cl-removal produced an immediate hyperpolarization (3-18 mV) and readdition of Cl-produced a transient depolarization (5-22 mV).3. The intracellular accumulation of Cl-was dependent on the external Clactivity. Even when the external Cl-concentration was reduced to 3 %, the cells accumulated Cl-against an electrochemical gradient.4. Cl-accumulation was temperature sensitive (Q10 -2). 5. On removal of external Na+, ai1 fell to a level which was close to that expected for passive distribution. The active reaccumulation of Cl-, after intracellular Cldepletion, was abolished in the absence of external Na'; a', slowly increased to its passive level. Steady-state a', or its recovery by Cl--depleted cells was not affected by the absence of K+ in the bathing solution.6. The reaccumulation of Cl-was not affected by furosemide (1-5 mM), bumetanide (10-4 M), amiloride (10-s M) or 4-acetamido-4'-isothiocyanostilbene-2,2'-disulphonic acid (SITS, 10-4 M).7. Removal of external Cl-caused a fall in intracellular Na+ activity (aNa, measured with Na+-selective microelectrodes) from 15-9 + 6-8 mm (n = 9) to 2-5 + 1-3 mm (n = 3). When external Cl-was readded, aia rose to 46-5 + 6-6 mm (n = 3) before slowly recovering towards its original value. The maximal change in aia was 41-7 + 45 mm (n = 3) and the rate constant for Na+ uptake was 1-8 + 0-4 min-'

Epithelial transport and osmoregulation in annelids

“…The cellular mechanisms of salivary-gland secretion have been well investigated using the salivary gland of the giant leech Haementeria ghilianii (Walz et al 1988). Wuttke and colleagues investigated the cotransport of Na + and Cl -and found that Cl -uptake is sodium-dependent and Cl -accumulates in the cells even against an electrochemical gradient (Wuttke and Berry 1990). They also analyzed pH regulation and its effects on salivary-gland secretion (Wuttke et al 1994).…”